Camera with a multi-zone focus detecting device

ABSTRACT

A camera with a multi-zone focus detecting device has an objective lens mounted on a camera. An image formed by the objective lens is divided into a plurality of zones. In each zone, a focusing condition is detected based on the image formed by the objective lens so as to produce a plurality of focusing condition data. Based on the result of the focusing conditions, one zone is selected. Furthermore, a light which has passed through the objective lens is measured separately in each zone so as to produce a plurality of measured light data. Based on a focusing condition data obtained from the selected zone, the objective lens is driven to an infocus condition. When the objective lens is driven to the infocus condition, a measured light data obtained from the selected zone is used for calculating exposure data with which the exposure is controlled.

This is a continuation of application Ser. No. 136,910 filed on Dec. 21,1987, which is a continuation of U.S. Ser. No. 050,739, filed on May 15,1987 now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the invention

The present invention relates to a multi-zone light measuring deviceand, more particularly, to camera having a focus detecting devicecapable of measuring object lights at a plurality of zones or at aplurality of points in the photographing frame and selecting an optimumvalue of the measured object light for use in exposure data indicationand exposure control.

2. Description of the Prior Art

Conventionally, a camera with a so-called spot light measuring device isknown. The spot light measuring device measures the brightness of asmall zone in the photographing frame so that a particular objectcaptured by the small zone can be properly exposed on the film. However,the prior art spot light measuring device employed in the camera is soarranged as to measure lights at a certain small zone located at thecenter of the photographing frame. Therefore, when it is desired tomeasure lights at a portion other than the center small zone, first, thecamera should be so held that the desired portion comes to the center ofthe photographing frame, and then, the spot light measuring is effected.The result of the spot light measuring is stored in a memory means.Thereafter, the camera is moved so as to bring the spot light measuredportion at a desired place in the photographing frame, and then theshutter release operation is carried out. In other words, according tothe prior art, it is necessary to carry out the AE lock operation orfreeze operation when it is desired to effect the spot measuring of aspot located off the center of the photographing frame.

However, such an AE lock operation or freeze operation as describedabove is complicated and troublesome. Moreover, in the case where atarget object is moving, it is very difficult to perform the AE lockoperation with respect to the moving target object, because it isdifficult to catch the moving object at the center of the photographingframe for a certain period of time. Furthermore, it is difficult to takepictures of a moving object not only when the moving object is to belocated off the center of the photographing frame, but also when themoving object is to be located at the center of the photographing frame.

SUMMARY OF THE INVENTION

Accordingly, an essential object of the present invention is to providean improved camera which can indicate and control the exposure amountwith respect to a target object on the basis of the object light valueobtained through the spot light measurement, regardless of the positionof the target object in the photographing frame, and without requiringsuch an operation as the AE lock, etc.

In accomplishing the above-described object, the camera according to thepresent invention is provided with a focus detecting means which detectsthe focus condition in a plurality of zones or at a plurality of pointsin the photographing frame, a measuring means for carrying out spotlight measurement(s) or in an area including the plurality of zones orpoints, a first selecting means for selecting, based on the result ofthe focus detection by the focus detection means, the zone in which apicture-taking lens is to be focused, a second selecting means forselecting the measured light value of a zone corresponding to the zoneselected by the first selecting means and, a means for displaying anexposure data and for controlling the exposure based on the measuredlight value selected by the second selecting means.

Although the term "spot light measurement" implies the light measurementeffected in a relatively small zone, the term "spot light measurement"employed herein should be read as including not only the spot lightmeasurement of a small zone, but also the spot light measurement of arelatively wide zone, so long as a part of the photographing frame ismeasured.

According to the present invention, the focus condition of apicture-taking lens is detected with respect to a plurality of zones orspots in the photographing frame. Of the plurality of zones or spots,one particular zone or spot such as the zone or spot aiming an objectlocated closest to the camera, is selected, and the picture-taking lensis driven automatically to an in-focus condition with respect to theobject in the selected zone or spot. Also, light measurement dataobtained through the spot measurement of an area corresponding to orcovering, the selected zone or spot is used for the display of theexposure data and for the exposure control.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects and features of the present invention willbecome apparent from the following description taken in conjunction witha preferred embodiment thereof, with reference to the accompanyingdrawings, in which:

FIG. 1a is a view explanatory of a zone for carrying out the focusdetection and an object light measurement, according to prior art;

FIG. 1b is a view explanatory of zones for carrying out the focusdetection and an object light measurement, according to one embodimentof the present invention;

FIGS. 2a-2d are views explanatory of an optical system employed in acamera according to the preferred embodiment of the present invention;

FIG. 3 is a block diagram showing an entire circuit employed in thecamera of FIG. 2;

FIG. 4 is a flow-chart showing an operation of a microcomputer employedin the circuit of FIG. 3;

FIGS. 5a and 5b taken together as shown in FIG. 5 show a flow-chart ofan operation of an AF microcomputer employed in the circuit of FIG. 3;

FIGS. 6-9 are flow-charts respectively showing operations of the datainitial processing routine, the initial correlation routine, the initialcorrelation low contrast detection routine and the priority settingroutine of the zones;

FIG. 10 is a flow-chart showing an operation of a precise correlationroutine according to the preferred embodiment of the present invention;

FIG. 11 is a modification of the flow-chart shown in FIG. 10;

FIGS. 12a and 12b are diagrammatic views respectively showing examplesof a structure of a CCD;

FIG. 13 is a circuit diagram showing one example of a driving circuitfor driving the CCD of FIG. 12a;

FIG. 14 is a timing chart showing an operation of the circuit of FIG.13;

FIG. 15 is a timing chart showing an integration procedure carried outfor a selected zone at step #27 of FIG. 5;

FIG. 16 is a circuit diagram showing an example of a driving circuit fordriving the CCD of FIG. 12b; and

FIG. 17 is a timing chart showing an operation of the circuit of FIG.16.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1a, a photographing frame in the viewfinder accordingto prior art is shown, in which a rectangular frame at the centerthereof represents a zone for effecting a focus detection and a spotlight measurement. In fact, the light measuring device and the focusdetecting device actually employed in the camera, according to prior arthave a sensitive zone located in a small area at the center of theviewfinder. Consequently, an automatic focus (hereinafter referred to asan AF) adjustment is carried out such that, a photographer first holds acamera so that the object to be photographed is spotted by the centerrectangular frame in the viewfinder, regardless of his or her intentionfor the framing, so that the target object to be photographed can bedetected for the adjustment by the focus detection sensitive zone of theAF device. Teen, the photographer locks the focus detected condition byan AF lock means. Then, the photographer is ready to take a pictureaccording to his or her desired framing. When a moving object is to beconsequently photographed, since it is very difficult to catch themoving object in the focus detection sensitive zone at all times withoutfailure, the target object moving at high speed often falls out from thefocus detection sensitive zone, resulting in an unstable operation ofthe AF device.

Accordingly, in order to solve the above-described disadvantages andinconveniences, the present invention provides an automatic focusingcamera which is, as shown in FIG. 1b, provided with a plurality of focusdetection sensitive zones. The spot light measuring zones are locatedcorrespondingly to the plurality of the focus detection sensitive zones.

It is statistically found out that the photographs at a high percentagehave the main object to be photographed located closest to the camera.Therefore, based on this fact, according to the automatic focusingcamera of the present embodiment, it is so arranged that a focusdetection sensitive zone detecting an object which is located closest tothe camera is automatically selected among a plurality of focusdetection sensitive zones. Based on the focus data obtained from theselected zone, the picture-taking lens is automatically focused to theclosest object, and at the same time, based on the spot lightmeasurement data obtained from the same selected zone, the display ofthe exposure data and the exposure control are carried out. Accordingly,the troublesome operation such as to obtain focus data and exposure databefore setting the camera to a desired aiming angle can be solved by thecamera of the present embodiment. According to the present embodiment,without framing the main object at the center of the photographing frameof the viewfinder, the automatic focus adjustment and the spot lightmeasurement of the main object can be carried out.

FIGS. 2a-2d show an optical system of the camera according to thepresent embodiment.

Referring to FIG. 2a, there is shown a schematic view of the opticalsystem according to one embodiment of the present invention applied to asingle lens reflex camera. In FIG. 2a, a part of the light having passedthrough a picture-taking lens 1 is reflected by a main mirror 2 and isdirected to a view finder section 5. The remaining light is passedthrough a translucent portion of the main mirror 2 and is reflected by asub-mirror 3 to direct light towards an automatic focus detecting module4. The light directed to viewfinder section 5 forms an image on a matsurface of a focusing screen 7 which is then outputted to aphotographer's eye through a pentagonal roof prism 9. A part of thelight directed to the viewfinder section is scattered by a diffractiongrating 8 and is completely reflected between top and bottom faces ofthe screen 7 and is guided to a spot light measuring element 10 disposedon the side surface of the screen 7.

FIG. 2c indicates the arrangement of the diffraction grating 8 and fourspot light measuring elements BV1-BV4 provided on the side surface ofthe focusing screen 7. The diffraction grating 8 has four sections whichare placed on mat surface of the screen 7 in a manner as shown in FIG.2c so that the light is scattered add guided in four differentdirections as indicated by arrows. The light measuring elements BV1-BV4are disposed at respective light emission outlets, i.e., at placesindicated by the arrows. The light having passed though main mirror 2and directed to the lower part of the camera body by sub-mirror 3further passes through an infrared light cut-off filter 11, a mask plate12 provided at a place approximately equal to a focal plane, a condenserlens 13, a mirror 14 and a pair of re-focusing lenses 15, therebyforming two images on a photoelectric converting element 16. A detaileddescription will be given hereinbelow with reference to FIG. 2b.

Referring to FIG. 2b, the light passed through infrared light cut-offfilter 11 reaches the mask plate 12 placed adjacent the focal plane.Mask plate 12 permits only the light in four zones, first zone, secondzone, third zone and fourth zone, to pass therethrough. The light frommask plate 12 in four zones passes through condenser lens 13, and isdeflected 90° by mirror 14. Then, the light is divided into two byre-focusing lenses 15, so that for each zone two images, a standardimage and a reference image, are formed on photoelectric convertingelement 16. More specifically: for the first zone, a standard image anda reference image are formed on standard area PAL1 and reference areaPAR1, respectively; for the second zone, a standard image and areference image are formed on standard area PAL2 and reference areaPAR2, respectively; for the third zone, a standard image and a referenceimage are formed on standard area PAL3 and reference area PAR3,respectively; and for the fourth zone, a standard image and a referenceimage are formed on standard area PAL4 and reference area PAR4,respectively. When the distance or deviation X_(z) (z=1 through 4)between the standard area PAL_(z) and a reference area PAR_(z) is equalto a predetermined deviation L_(z), it is determined that the object isin the in-focus condition. When the deviation X_(z) is larger thanL_(z), it is determined that the object is in the rear-focus conditionin which the object is located too close to the picture-taking lens withrespect to the infocusing condition of the lens. On the contrary, whenthe deviation X_(z) is smaller than the deviation L_(z), it isdetermined that the object is in the front-focus condition in which theobject is located too far away from the picture-taking lens with respectto the infocusing condition of the lens. When the optical system of FIG.2b is developed, it will be as shown in FIG. 2d.

An electric circuit arrangement of the camera according to the presentembodiment is shown in FIG. 3.

The camera of the present embodiment is controlled by twomicroprocessors, i.e., a microprocessor COP which controls the entirecamera (referred to as a camera-control microcomputer hereinafter) and amicroprocessor AFP which controls the automatic focusing (hereinafterreferred to as an AF microcomputer). A reference character Sl designatesa switch for starting the measurement of the object light and the AFautomatic focusing operation; S2 designates a release switch foreffecting the film exposure, thereby starting the photographingoperation of the camera; S4 designates a switch which is turned off whenthe main mirror and a shutter curtain of a focal plane shutter arecharged, and is turned on after the completion of the exposure. A signalto open or close each of the above-described switches is inputted to thecamera-control microcomputer COP.

An output generated from each of the spot light measuring elementsBV1-BV4 is selectively outputted by a selecting signal AEMPS from thecamera-control microcomputer COP in a multiplexer AEMP and, inputted tothe camera-control microcomputer COP in the form of a digitalized valueby an A/D converting circuit AEAD. The camera-control microcomputer COPreceives, from a lens data outputting circuit LDM, data LDS which isnecessary for the AF control. Data LDS includes the conversioncoefficient for converting the defocus amount detected in an automaticfocus detecting part to an appropriate amount corresponding toindividual lenses by which the lens is focused, the maximum aperturevalue of the lens, the minimum aperture value of the lens, etc. Of thedata LDS, only the data necessary for the AF control are transferred tothe AF microcomputer AFP.

The camera-control microcomputer COP receives data from an ISO dataoutputting means SVM, which produces the film sensitivity data on theApex value Sv. The camera-control microcomputer COP calculates theexposure data on the basis of the inputted data, and produces anexposure value signal AES to an exposure display AED for displaying theexposure data. Furthermore, after a release signal for the releaseswitch S2 is applied to the camera-control microcomputer COP, thecamera-control microcomputer COP outputs an exposure controlling signalBCS to an exposure control BCR, thereby controlling the exposure.

AF (automatic focusing) microcomputer AFP drives an AF sensor composedof CCDs through an AF interface AFIF. An output from the AF sensor CCDis processed in the analog form and is converted to the digital form bythe AF interface AFIF, such that the digitalized image information isapplied to the AF control microcomputer AFP which, in response to thereceipt of the digitalized image information, carries out the AFcalculation to obtain the de-focus amount.

Furthermore, the AF control microcomputer AFP converts the de-focusamount to the shifting amount of the lens on the basis of the lens datasupplied from the camera-control microcomputer COP, whereby a motordriver MDR drives a motor MO by an amount corresponding to the lensshifting amount. While motor MO is being driven, the rotating amount ofthe motor is detected by an output signal DCL from a motor encoder ENC,which is also fed back to motor driver MDR.

Moreover, AF control microcomputer AFP is arranged to indicate thein-focus condition by outputting an in-focus signal FAS to an in-focusdata display device FAD, for the purpose of confirmation of the in-focuscondition, etc.

The signal exchange between the camera-control microcomputer COP and theAF microcomputer AFP will be described hereinbelow. An AF starts signalAFST sent from the camera-control microcomputer COP to AF microcomputerAFP is for starting the AF operation. In FIG. 3, a bar extending overAFST indicates that AF microcomputer AFP starts the AF operation inresponse to the change of the AF start signal AFST from a HIGH level toa LOW level.

When an AF end signal AFE sent from AF microcomputer AFP tocamera-control microcomputer COP is changed from a LOW level to a HIGHlevel, it is indicated that the AF operation is completed and that thein-focus condition is obtained. A pulse signal, AF stop signal AFSP, issent from camera-control microcomputer COP to AF microcomputer AFP so asto stop the AF operation.

Moreover, an AF zone selecting signal AFZS, when it becomes a HIGHlevel, indicates that one of the four zones described above is selected.A signal SZS represents the selected zone. A data bus LDT is providedfor transmitting AF lens data to the AF microcomputer AFP only the datanecessary for the AF operation among the lens data LDS inputted fromlens data outputting circuit LDM by camera-control microcomputer COP.

With reference to the flow-charts shown in FIGS. 4, 5a and 5b, theoperation of the above-described circuit will be described particularlywith respect to the camera-control microcomputer COP and the AFmicrocomputer AFP.

When a release button is depressed halfway, switch Sl turns on, so thatan interrupting signal is added to an interruption terminal INT0 ofcamera-control microcomputer COP (step #1 in FIG. 4). This interruptionsignal enables camera-control microcomputer COP, i.e., drives cameracontrol microcomputer COP out of the stop mode, so that start signalAFST is changed from a HIGH level to a LOW level, thereby activating theAF control microcomputer AFP (step #2 in FIG. 4) to start the lightmeasuring operation (step #3 in FIG. 4). Then, camera-controlmicrocomputer COP receives data necessary for calculating the exposure,such as, Sv data from ISO data outputting means SVM and various lensdata LDS from lens data outputting means LDM (step #4 in FIG. 4). Amongthem, only the lens data necessary for the AF operation are furthertransmitted to AF control microcomputer AFP (step #5 in FIG. 4). Thelight measurement data are inputted to camera-control microcomputer COPfrom AF control microcomputer AFP at step #6.

Thereafter, camera-control microcomputer COP determines whether or notthe AF zone selecting signal AFZS from AF microcomputer AFP is changedto a HIGH level (step #7 in FIG. 4). The AF zone selecting signal AFZS,which will be further described in detail later, is in a LOW level stateat the beginning of the operation.

When the AF zone selecting signal AFZS is at a LOW level (indicatingthat any AF zone has not yet been selected), camera-controlmicrocomputer COP calculates an average of the light measuring dataBV1-BV4 and takes the average as the measured value (step #8), andfurther carries out an exposure calculation based on each data (step #11in FIG. 4). Upon completion of the exposure calculation, camera-controlmicrocomputer COP produces the result of the calculation to the exposuredisplay device AED for the display (step #12). After the above-describedoperations in one loop are completed, it is detected whether or notswitch Sl is continuously depressed (step #13). If switch Sl is keptdepressed, it is checked whether or not the shutter is completelycharged (step #14) and whether or not the infocus condition is obtained(step #15).

If the results of both steps #13 and #14 are YES, an interruption fromthe interruption terminal INTl is permitted so that the shutter releasecan be effected (step #16). Thereafter, the program is returned to step#4 in which the data are inputted again.

On the other hand, if at least on of the results of steps #13 and #14 isNO, the program returns back to step #4 without passing through step #16so that the shutter release permission cannot be given. If switch Sl isnot depressed at step #13, the light measurement and the display of theexposure are stopped at steps #17 and #18, with the AF stop signal AFSPbeing outputted so as to stop the AF operation at step #19, and also theAF start signal AFST being brought into a HIGH level at step #20. Then,the interruption from the interruption terminal INT0 is permitted atstep #21, while the interruption by the terminal INTl from switch S2 isprohibited at step #22. Then, a flag BIF is reset at step #22-1, andthus the AF operation is stopped, i.e,. AF microcomputer AFP enters thestop mode.

On the other hand, AF microcomputer AFP starts the operation when thestop mode is interrupted as the AF start signal AFST sent from thecamera-control microcomputer COP is applied to an interruption terminalINTA of AF microcomputer AFP (step #30 in FIG. 5a). When AFmicrocomputer AFP starts the AF operation, the AF end signal AFE isdropped to a LOW level and also the AF zone selecting signal AFZS isdropped to a LOW level, so that AF microcomputer AFP provides a signalto camera-control microcomputer COP indicating that the AF zone has notyet been selected, and at the same time, the AF microcomputer AFP resetsa flag LDF, which flag is set when the lens is driven (step #31 in FIG.5a).

Next, after the CCD is initialized (step #32 in FIG. 5a), a variable Z,representing the AF zone number, is set as "4" (step #33), and the lensdata LDTS necessary for the AF operation is inputted from thecamera-control microcomputer COP (step #34). Then, the CCD iscontrolled. First, the integration of the CCD is effected. When theintegrated light amount reaches a proper level, or when a predeterminedmaximum integration time lapses as occurred when the brightness of theobject to be photographed is relatively low, a shift pulse is applied tothe CCD. Accordingly, the data of the CCD, namely, the image informationin the digital form is inputted (step #35 in FIG. 5a). Although theoperation will be described more in detail later, it is to be noted herethat the data from the CCD in all the zones 1-4 are inputted.

A low contrast flag, used for indicating whether or not the object to bephotographed has a low contrast, is set (step #36 in FIG. 5a). The lowcontrast flag is cleared only when the focus detection effected at thepreceding CCD integration was possible. In this situation, since the CCDintegration is carried out for the first time, the low contrast flag isset. The flag will be utilized later so as to decide whether thelow-contrast scans should be carried out, or whether the in-focusdetection should be carried out again with the lens being remained inthe position as it is. It is to be noted here that the low-contrast scanis an operation effected when the contrast of the object to bephotographed is relatively low, and is carried out such that the lens isdriven all over the driving range thereof, for example, in onereciprocal movement to find a position which can provide a propercontrast of the object.

In order to decide the priority of the four zones for the focusdetection calculation, a data initial processing (steps #37-#57), aninitial correlation (steps #57-#72), an initial correlation low contrastdetection (steps #73-#81) and a priority setting of the zones (steps#83-#94) are carried out. These operations will be described later indetail, but in brief, the operations are such that, the zone includingthe closest object among the objects within the photographing frame, inother words, the zone having the largest image deviation among imagedeviations L1, L2, L3 and L4 (FIG. 2d) calculated in each zone isselected and the focus detection is effected only with respect to theparticular zone. This is because, if the precise correlation calculationis conducted for all of the zones, the calculation time may beundesirably prolonged.

It is checked in step #82 whether or not the variable Z is "0", and ifthe variable Z is "0", it is decided that all of the AF zones are in lowcontrast.

The determination of the low contrast at this stage of the operation isperformed in a simple manner as described above in a small range ofdetermination because the determination of the low contrast will becarried out again after the precise correlation. With respect to thezone selected by the initial correlation, the in-focus conditiondetection calculation is further carried out with more accuracy in theprecise correlation calculation (steps #96-#105). Based on the aboveprecise correlation calculation, the low contrast check is furtherperformed (steps #106, #107). When the selected zone has a low contrast,the program goes through steps #108 and #111, and carries out theprecise correlation calculation (steps #96-#105) for another zone. Thesteps #108, #111, #96-#105 are repeated, so that the contrast conditionsin the zones are detected in turns in the priority order as determinedin steps #83-#94 until a zone with a sufficient contrast is found. If azone with a sufficient contrast is found, the program goes to step #112for the defocus amount calculation. If all of the four zones has a lowcontrast, the program goes to step #109. At step #109, if the lowcontrast flag s set, the situation is assumed that the lens isconsiderably away from the in-focus position with respect to the objectto be photographed, and therefore it is considered that the detection ofthe de-focus amount is not possible. In such a situation, a low contrastscan operation (step #110) is carried out by one reciprocal movement ofthe lens between the nearest focusing position to the infinite focusingposition. During the reciprocal movement of the lens, the CCDintegration and the calculation are repeated many times so as to searcha lens position at which the defocus amount can be detected.

When it is detected that the zone is not in the low contrast and thede-focus amount is calculated (step #112), the low contrast flag iscleared (step #113), and this situation of the lens is stored. Thus evenif it is detected in the next integration that the zone has a lowcontrast, the integration and calculation of the CCD are carried out inall the zones with the lens remained as it is. By so doing, even if heaiming object moves from one zone to another without a substantialchange in the distance between the object and the camera, the lowcontrast scanning will not be carried out just because that the zone asselected in the previous cycle is now in the low contrast condition.Thus, it is possible to prevent the lens from losing its position as theresult of the low contrast scanning.

Thereafter, in order to inform camera control microcomputer COP of thelight measuring zone as selected by AF control microcomputer AFP, a zonesignal SZS representing the zone selected by AF control microcomputerAFP is transferred to camera-control microcomputer COP, and then the AFzone selecting signal AFZS changes its state to a HIGH level at step#114. Thereafter when the operation in camera-control microcomputer COPcomes to step #7, the program goes to step #7-1 and further to step #9,so that the AF zone signal SZ is inputted in order to conduct the spotlight measurement calculation based on the signal obtained from thelight measuring element corresponding to the selected zone (step #10).This is explained in detail hereinbelow.

If the AF zone selecting signal AFZS is detected as in a HIGH level instep #7 in FIG. 4, it is further detected in step #7-1 whether or notthe AF end signal AFE is HIGH. Then, when the AF end signal AFE is HIGHindicating that the in-focus condition is obtained, it is furtherdetected at step #7-2 whether a flat BIF is set or not. In the casewhere the flag BIF is not set, the flag BIF is set at step #7-3. Then,the program proceeds to step #9. On the contrary, in the case where theflag BIF is set, the program goes to step #11, without changing the Bvcin step #10. As apparent from the above, the light measuring data of thezone (identified by the AF zone selecting signal AFZS) selectedimmediately after the lens has reached the in-focus condition is AElocked. If the AF end signal AFE is found not to be HIGH in step #7-1indicating that the lens has not reached the i-focus condition, the flagBIF is reset in step #7-4. Then, the program goes to step #9.

Thereafter, the AF control microcomputer AFP detects whether or not thecalculated de-focus amount is within the predetermined in-focus zone(step #115). When it is detected that the lens is positioned within thein-focus zone, the AF microcomputer AFP changes the AF end signal AFE tobe HIGH, indicating the completion of the AF operation to camera-controlmicrocomputer COP, together with the display of the in-focus condition,and permitting the shutter release (steps #121 and #123).

In contrast, when it is detected at step #115 that the lens is out ofthe in-focus zone, the shifting amount of the lens is calculated (step#116) in the form of a number of pulse LEP to be counted by the encoderENC with the use of the conversion coefficient with which the de-focusamount is converted to the lens shifting amount inputted previously.Motor MO is accordingly driven by the number of the calculated pulsecounts which number is counted by a counter PC (steps #117, #118 and#119), thereby to move the lens by the calculated lens shifting amount,and then the motor is stopped (step #120).

After the above-described operation, the integration of the CCD iscarried out again in order to check again whether or not the lens isproperly focused. At this time, to shorten the operating time, theintegration is carried out only in the selected CCD zone through thepreceding calculation (step #127). Before this, the variable Z is set tobe "1", and the data LDTS necessary for the AF operation is inputted toAF microcomputer AFP (steps #125 and #126) so that the low contrastdetection can be carried out only in the selected CCD zone. Then, theprecise correlation calculation only with respect to the selected CCDblock is conducted, and the lens is shifted in accordance with theresult of the focus detection. If it is detected at this stage that theselected CCD is in the low-contrast, the lens is held in the position asit is, and the operations from the integration of the CCD in all zonesare repeated without moving the lens.

The foregoing description is related to the fundamental operation of theautomatic focusing camera provided with an automatic focus adjustingmeans which adjusts the focusing condition of the lens irrespective ofthe position of the target object in the photographing frame and, anexposure control means which controls the exposure by the spot lightmeasurement with respect to the target object.

Next, the description is directed to the details of the operations forthe data initial processing (FIG. 6), the initial correlation (FIG. 7),the initial correlation low-contrast detection (FIG. 8) and the prioritysetting of the zones (FIG. 9), which are arranged from a viewpoint ofreducing the calculation time.

First, the data initial processing routine will be described inconnection with FIG. 6. At step #37, a zone data Z is set to be "1"identifying one of the four AF zones. At step #38, a cumulative contrastdata C(Z) is set to be "0" indicating a cumulative contrast value to bezero at the beginning, and at step #39, a cycle number data j indicatingthe number of contrast calculation cycles carried out for one AF zone isset to be "0".

Then, at step #40, a difference of the A/D converted data between twoadjacent picture elements in the standard area in the CCD is taken, andthe difference is checked whether it is positive or negative. Each timethe difference is checked, sign data Ld_(j) holds "1" (step #41) or "0"(step #42) when the detected result is positive or negative,respectively. More specifically, when each picture element in thestandard area is producing a data LD_(j), a calculation:

    LD.sub.j (Z)-LD.sub.j+l (Z)                                (1)

is carried out in step #40, a result of which is judged whether it ispositive or negative. In the case where the result is positive, the signdata Ld_(j) is made "1" in step #41, while in the case where the resultis negative, the sign data Ld_(j) is made "0" in step #42.

The same calculation as formula (1) is carried out in step #43, and theobtained difference represents a contrast value C. An absolute value |C|is taken and is added to a cumulative contrast value C(Z) (step #44),thereby obtaining a sum of the absolute values |C|s up to the presentcalculation cycle. Then the cycle number data j is increased by "1" instep #45. The operations of steps #38-#45 are repeated until the cyclenumber data j becomes (k-1) (k is the number of picture elementsprovided in the standard area) (step #46).

Therefore, by repeating steps #40-#46 for (k-1) cycles, sign data Ld₁(1), Ld₂ (2), . . . , Ld_(j) (1), . . . and Ld_(k-1) (1) are stored inAF microcomputer AFP which represent a contrast change distributingalong the standard area in the first AF zone, and at the same time, thecumulative contrast value C(1) is also stored. Similar data will bestored for the second, third and fourth AF zones, as described below.

When the cycle number data j becomes equal to (k-1) in step #46, it isdetected in step #47 whether or not the zone data Z representing the AFzone number is "4". In this manner, the operations of steps #38-#45 foreach one of the four AF zones are carried out. In the case where thezone data Z is not "4", the zone data Z is added with "1" in step #48,so that the operation returns to step #38. The operations in step#38-#47 will be repeated until the zone data Z becomes "4k", i.e., untilfour standard areas are processed. Accordingly, data representing thecontrast change distribution an the cumulative contrast value are storedfor each of the first, second, third and fourth AF zones.

When the zone data Z becomes "4" in step #47, the program advances tostep #49. In steps #49-#57, operations similar to steps #37-#47(excluding steps #38, #43 and #44) are carried out. In steps #49-#57,four reference areas are processed. It is to be noted here that, insteps #49-#57, instead of the sign data Ld_(j), a sign data Rd_(j) isused for holding "1" or "0" for the indication of positive or negativeof the obtained difference between two neighboring picture elements inthe reference area. Also, l, which is greater than k, represents thenumber of the picture elements provided in the reference area.

Thus, in the manner described above, for the first to fourth standardareas, the cumulated contrast values C(Z) ((Z=1 through 4) and thecontrast change distributions:

Ld₁ (Z), Ld₂ (Z), . . . , Ld_(j) (Z), . . . and Ld_(k-1) (Z)

are obtained, and for the first to fourth reference areas, the contrastchange distributions:

Rd₁ (Z), Rd₂ (Z), . . . , Rd_(j) (Z), . . . and Rd_(l-1) (Z) (l isgreater than k)

are obtained, thereby completing the initial processing operation (FIG.6).

Referring to FIG. 7, the initial correlation routine will be described.At step #58, the zone data Z is set to be "1" identifying one of thefour AF zones. At step #59 a shift data n is set to be "1", at step #60a correlation data hn(Z) is set to be "0", and at step #61 the cyclenumber data j is set to be "0" indicating the number of contrastcalculation cycles carried out for one AF zone.

At step #62, a calculation

    Ld.sub.j (Z)-Rd.sub.j+(n-l) (Z)                            (2)

is carried out to obtain a difference between the contrast changedistribution of the standard area and that of the reference area.

More specifically, for the first (k-1) cycles of operations throughsteps #62-#65, since shift data n=1, a difference between the contrastchange distribution:

Ld₁ (1)d, Ld₂ (1), . . . , Ld_(j) (1), . . . and Ld_(k-1) (1) of thestandard area and the contrast change distribution:

Rd₁ (1), Rd₂ (1), . . . , Rd_(j) (1), . . . and Rd_(k-1) (1)

of the reference area is obtained. To this end, a difference betweensign data Ld_(j) in the standard area and the sign data Rd_(j) in thereference area is calculated at step #62 as indicated below:

Ld₁ (Z) - Rd₁ (Z)

Ld₂ (Z) - Rd₂ (Z)

Ld₃ (Z) - Rd₃ (Z)

Ld_(k-1) (Z) - Rd_(k-1) (Z) In each subtraction, if the difference isequal to zero indicating the concordance between sign data Ld_(j) andRd_(j), the program proceeds to steps #64 and #65 so as to carry out thenext subtraction. On the contrary, if the difference is not equal tozero indicating the discordance between sign data Ld_(j) and Rd_(j), theprogram follows step #63 to count the number of occurrences of such adiscorance in each comparison between the contrast change distributionsLd_(j) (Z) and Rd_(j) (Z). The counted result is stored as thecorrelation data h(Z).

When the correlation data hn(Z) has a great number, indicating that thediscordance occurred many times, it can be said that the correlation islow or poor. On the other hand, when the correlation data hn(Z) has asmall number, indicating that the discordance occurred only a few times,it can be said that the correlation is high or good.

When (k-1) cycles of operations through steps #62-#65 are carried out,the program goes to step #66, at which it is detected whether n=1 ornot. At this stage, since shift data n=1, the program goes to step #68at which the correlation data hn(Z) is stored as a minimum correlationdata Mhn(Z), and also, (n-Lz is stored as an image deviation data Mn(Z).Here, an amount Lz represents a predetermined shift amount to obtain aproper infocus condition. Thus, (n-Lz) represents an amount of defocus.

At step #69, shift data n is increased by "1", such as to "2" at thisstage, and at step #70, it is detected whether or not n is equal to(l-k+2). If not, the program returns to step #60 at which thecorrelation data hn(Z) is cleared to "0", and at next step #61, thecycle number data j is also cleared to "0".

Then, for the next (k-1) cycles of operations through steps #62-#65,since shift data n=2, a difference between the contrast changedistribution:

Ld₁ (1), Ld₂ (1), . . . , Ld_(j) (1), . . . and Ld_(k-1) (1)

of the standard area and the 1-bit shifted contrast change distribution:

Rd₂ (1), R₂ (1), . . . , Rd_(j+1) (1), . . . and Rd_(k) (1)

of the reference area is obtained. To this end, a difference betweensign data Ld_(j) in the standard area and 1-bit shifted sign dataRd_(j+1) in the reference area is calculated at step #62 as indicatedbelow:

Ld₁ (Z) - Rd₂ (Z)

Ld₂ (Z) - Rd₃ (Z)

Ld₃ (Z) - Rd₄ (Z)

Ld_(k-1) (Z) - Rd_(k) (Z)

In the same manner as described above, during the above subtractions,the number of occurrences of the discordance is counted in step #63, andthe counted result is stored a the correlation data hn(Z).

Then, at step #66, it is detected whether or not n=1. At this stage,since n=2, the program goes to step #67 at which it is detected whetheror not the newly obtained correlation data hn(Z) is equal to or smallerthan the minimum correlation data Mhn(Z) as so far obtained. If thenewly obtained correlation data hn(Z) is smaller than the presentminimum correlation data Mhn(Z), the program goes to step #68 to storethe newly obtained correlation data hn(Z) as the minimum correlationdata Mhn(Z), and also the image deviation data Mh(Z) is rewritten. Onthe contrary, at step #67, if the newly obtained correlation data hn(Z)is not smaller than the previously obtained minimum correlation datahn(Z), the program goes to step #69 to increase the shift data n by "1".

In this manner, for one zone, after every one bit shift, the comparisonbetween the contract change distribution along the standard area and thecontrast change distribution along the reference area is carried out.Therefore, in total, the comparison is carried out for n(=l-k+2) timesfor one zone.

The above operation (steps #59-#70) is carried out for four zones, sothat the minimum correlation data Mhn(Z) (n is between 1 and l-k+2 and Zis 1, 2, 3 or 4) and the image deviation data Mh(Z) are obtained foreach of the four zones, thereby completing the initial correlationoperation (FIG. 7), and making it possible to start the initialcorrelation low contrast detection operation.

Referring to FIG. 8, the initial correlation low contrast detectionroutine is shown, in which the low contrast detection is carried outusing the calculation result of the cumulative contrast value C(j)obtained from the data initial processing operation (FIG. 6) and theminimum correlation data Min(j) obtained from the initial correlationoperation((FIG. 7). In the flow chart of FIG. 8, the variable j is usedfor representing the zone number which is first set to be "1" at step#73 so as to carry out the low contrast detection with respect to eachof the four AF zones. Since step #73 is preceded by step #71 (FIG. 8),the variable Z is now carrying "4". It is detected at step #74 whetheror not the cumulative contrast value C(1) for the first AF zone is overa predetermined value CS. At step #75, it is detected whether or not theminimum correlation data Mhn(1) is less than a predetermined value SM.

In the case where the cumulative contrast value C(1) exceeds thepredetermined value CS and at the same time, the minimum correlationdata Mhn(1) is less than the predetermined value SM, it is so detectedthat the focus detection can be carried out for the first AF zone, andaccordingly, a low contrast zone flag LZF(1) for the first AF zone isreset to be "0" at step #76.

On the other hand, if the contrast value C(1) is under the predeterminedvalue CS, or if the minimum correlation data Mhn(1) is over thepredetermined value SM, the variable Z which is initially carrying "4"is reduced to "3" at step #78, and also, it is so detected at step #79that the focus detection is not possible for the first AF zone, so thatthe low contrast zone flag LZF(1) for the first zone is set to be "1".

At step #80, it is detected whether j=4 or not. If not, then at step#81, the cycle number data j is increased by 1, and the program returnsto step #74 to repeat the steps #74-#79. At step #80, when j=4, theprogram goes to step #82 detecting whether Z=0 or not. Since Z isdecreased from "4" each time the program advances through steps #78 and#79, Z is now carrying a number equal to the number of reset lowcontrast flags. When there is at least one reset low contrast flag,meaning that there is at least one zone for which the focus detectioncan be carried out, the program goes to the flow chart of FIG. 9 atwhich the priority setting of the zones is carried out. On the contrary,when there is no reset low contrast flag, meaning that all four zone areso out of focus that the focus detection can not be carried out, theprogram goes to step #109 (FIG. 5a) to carry out the low contrast scan.

Referring to FIG. 9, a flow chart for setting the priority of zones isshown. At step #83, the zone number data j to be "1", registers M1, M2,M3 and M4 for storing the image deviation data are stored with theminimum image deviation -Lz and a cycle number data Q is set to be "0".At step #84, it is detected whether the low contrast flag LZF(1) for thefirst zone is reset, or not. If not, meaning that the first zone is soout of focus that the focus detection can not be carried out, then it isnot necessary to provide any priority to such a zone. In this case, theprogram goes to step #94 to add "1" to zone number data j so as todetermined the next low contrast flag, e.g., LZF(2). If the second lowcontrast flag LZF(2) is reset, then the program advances to step #85 atwhich it is detected whether or not the image deviation data Mn(2) forthe second zone is greater than the minimum image deviation -Lz. At thisstage, obviously the data Mn(2) is greater than the minimum imagedeviation -Lz as stored in register Ml. Therefore, the program goes tostep #86 at which the data in register M3 is shifted to register M4, thedata in register M2 is shifted to register M3, the data in register Mlis shifted to register M2, and the image deviation data Mn(2) is storedin register Ml in which the highest image deviation data is stored.Similarly, a register Bl is stored with "2" indicating the zone numberhaving the highest priority. Other registers B2, B3 and B4 are storedrespectively with the data previously stored data, such as "0", inregisters B1, B2, and B3. Then at step #92, the cycle number data Q isincreased by "1". Then, at step #93, it is detected whether Q=Z (Z isnow carrying a number equal to the number of reset low contrast flags),or not. If not, then the zone number data j is increased by "1", such asto "3", and the program returns to step #83.

At step #84, if the third low contrast flag LZF(3) is reset, then theprogram advances to step #85 at which it is detected whether or not theimage deviation data Mn(3) for the third zone is greater than the imagedeviation Mn(2) as stored in register Ml.

At step #85, if the data Mn(3) is greater than Mn(2), the programadvances to step #86 at which the data Mn(3) is store in register Ml,and the data Mn(2) is shifted to register M2. Similarly, the presentzone number data j, i.e., "3" is stored in register B1, and the zonenumber data "2" previously stored in register B1 is shifted to registerB2, indicating that the third zone has the first priority and the secondzone has the second priority.

On the contrary, at step #85, if the data Mn(3) is not greater thanMn(2), the program advances to step #87 at which the data Mn(3) iscompared with the minimum image deviation -Lz as stored in register M2.Obviously, the data Mn(3) is greater than the minimum image deviation-Lz as stored in register M2. Therefore, the program goes to step #88 atwhich the data in registers M2 and M3 are shifted to registers M3 andM4, respectively, and register M2 is stored with the data Mn(3).Similarly, register B2 is stored with the present zone number data j,i.e., "3" indicating that the third zone has the second priority.

In this manner, the zones carrying the reset low contrast flag are givenwith the priorities, and the first priority is given to the zone whichhas the smallest image deviation data, i.e., the zone receiving an imageof an object located closed to the camera.

Although the camera of the present embodiment has been described abovewith the description related to the initial processing, initialcorrelation, initial correlation low contrast detection and prioritysetting of the zones, the same function as the above can be achieved insuch a manner as that, instead of the calculation (subtraction) in step#97 in FIG. 10 to obtain the precise correlation value of the precisecorrelation or the initial processing in which the CCD data is binarizedby a predetermined value or an average output value of the CCD data,etc., an exclusive logic sum of the two data may be obtained, and theshift position is searched at which the above exclusive logic sumbecomes the minimum value, so as to effect the initial correlation.

Referring to FIG. 10, the procedure for the precise correlation will bedescribed in detail.

For the precis correlation value, it is obtained by the sum of theoutput differences, which are not binarized of outputs of the pictureelements in the standard area and the reference area of the zone, as inthe case of the initial correlation. More specifically, when eachpicture element in the standard area of the zone B_(i) having thehighest priority is producing data LD_(j), and each picture element inthe reference area of the zone B_(i) is producing a data RD_(j), theprecise correlation value H(p) is obtained as follows, ##EQU1## providedthat p changes from 1 to l-k+1. Therefore, l-k+1 precise correlationvalues H(p) are obtained through shifting of the reference area pictureelements, one bit at a time, for l-k+1 times with respect to thestandard area picture element array (steps #96-#99). When l-k+1 precisecorrelation values H(p) are obtained, the one H(PM) that has the minimumvalue is searched (step #101). Thereafter, in step #102, it is detectedwhether or not the shift amount PM is either one of "1" and l-k+1.

When the shift amount PM is neither "1" and l-k+1, the program goes tostep #103 in which an interpolation calculation result is subtracted byan image deviation LB_(i) of in-focus condition so as to obtain an imagedeviation XM.

The interpolation calculation is disclosed in detail in U.S. Pat. No.4,636,624 of Ishida et al. Therefore, its detail will not be explainedherein.

Furthermore, in step #104, the minimum precise correlation value YM isobtained.

On the contrary, in step #102, when the shift amount is either "1" or"l-k+1", the interpolation calculation can not be carried out.Therefore, the image deviation XM is set to be equal to the shift amountPM obtained in step #101, and also the minimum value H(PM) calculated instep #101 is regarded as the minimum precise correlation value YM.

Since the image deviation having the minimum precise correlation valuecan be anticipated from he result Mn(B_(i)) obtained in the initialprocessing, it is possible to shorten the calculation period if thecalculation is performed only with respect to those adjacent theanticipated image deviation within the selected zone B_(i).

Based on the minimum precise correlation value YM and the imagedeviation PM obtained in the above described manner, the low contrastdetection is carried out again, if necessary. Here, the condition issuch that the minimum precise correlation value YM divided by thecontrast value obtained in the initial processing is smaller than apredetermined value A (step #106-1). If the divided value is greaterthan the predetermined value A, the selected zone is regarded as the lowcontrast zone, and therefore, the program goes to step #108.

At step #106-2, it is detected whether the operation upto step #128 hasbeen carried out at leas for once, or not. If yes, in which case a flaghas been set at step #128, the program goes to step #107 to detectwhether or not an absolute value of the image deviation XM is smallerthan a predetermined value D. If XM is smaller than D, the program goesto step #112 so that the lens is driven based on the image deviation XM.However, if XM is greater than D, it is so assumed that since the imagedeviation XM is changed abruptly (over the predetermined value D), theobject must have been moved out from the selected zone. In such a case,the program goes to step #108 to carry out the CCD integration from thebeginning for all the zones.

Since the initial correlation is a simple correlation, there may be acase in which the defocus amount calculated in the initial correlationis greatly different from that obtained from the precise correlationwith respect to a particular image. In such a case, it may be possiblyhappen that an object located more close to the camera is in a zoneother than the selected zone. Therefore, in order to positively pick theclosest object, the following step are carried out.

At step #106-3, a variable q, which is initially zero, is increased to"1". Then, at step #106-4, it is detected whether or not q=1. If q=1,indicating the first cycle of the operation, the program goes to step#106-5 at which the image deviation Mn(B_(j)) obtained in the initialcorrelation is subtracted by the image deviation PM obtained in theprecise correlation, and it is detected whether or not the differencetherebetween is less than "1" picture element pitch. If the differenceis greater than "1" picture element pitch, the program goes to step#106-6 to store the image deviation XM and the selected zone numberB_(i) in registers ZM and Br, respectively. Thereafter, the program goesto step #108. Then, after repeating the another cycle of operation, andwhen step #106-3 is entered for the second time, the variable q isincreased to "2". Thus, the program advances from step #106-4 to step#106-7 in which the newly obtained image deviation XM is compared withthat stored in register ZM. If the newly obtained image deviation XM isgreater, the program goes to step #112 to drive the lens based on thenewly obtained image deviation XM. On the contrary, if the newlyobtained image deviation XM is smaller, the program goes to step #106-8at which the newly obtained image deviation XM and the zone number B_(i)are replaced with those obtained in the previous cycle as stored inregisters ZM and Br (step #106-8). Then, at step #112, the lens isdriven based on the previous data. At steps #106-7 and #106-8, the datahaving a greater image deviation is selected so the the close object canbe selected. At step #106-5, if the difference is less than "1" pictureelement pitch, the program goes to step #112 to drive the lens.

Referring to FIG. 11, a flow chart similar to that shown in FIG. 10 isshown. The only difference is in step #106-5' in which the subtractionis conducted by the use of the image deviation Mn(B_(j+1)) selected inthe initial correlation not as a primary, but as a secondary.

The flow of the whole operation in the camera according to the presentembodiment has been fully describe above. Hereinbelow, the detailedconstruction of the electric circuit, the AF sensor CCD and the AFinterface AFIF will be described now.

Referring to FIGS. 12a and 12b, two examples of the CCD which is used asan AF sensor in the present embodiment are shown. FIG. 12a shows anexample in which CCD output registers are arranged in series (thisarrangement is fully described in detail for example in U.S. patentapplication Ser. No. 005,413, assigned to the same assignee as thepresent application), while FIG. 12b shows an example in which CCDoutput registers are arranged in parallel, each CCD being formed byone-chip.

The construction common to the examples of FIGS. 12a and 12b will firstbe described. An image in the first to fourth blocks is divided to beformed on the standard area photodiode arrays PAL1-PAL4 as standard areaimages, and on the reference area photodiode arrays PAR1-PAR4 asreference area images. It is to be noted here that each of thephotodiode arrays includes an accumulation part corresponding to thediode array. The standard area photodiode array has k picture elements,while the reference area photodiode array has m picture elements (k<m).Adjacent to each of the standard area photodiode arrays PAL1-PAL4, thereare disposed respective photodiodes MP1-MP4 for monitoring thebrightness of the object to be photographed so as to control theintegration time of the CCD. The photocurrent generated in thephotodiodes MP1-MP4 discharges the electric charge of respectivecapacitors C1-C4, which has been charged approximately up to the levelof the source current in response to an integration clear gate pulseICG, at a rate proportional to the amount of the incident light. Thevoltages across the capacitors are taken out, through buffers having ahigh impedance input and a low impedance output, and outputted asmonitor outputs AGCOS1-4.

The integration clear gate pulse ICG is applied to a MOS gate providedbetween the accumulation part (photodiode array) and the power source.While the integration clear gate pulse ICG is in a HIGH level, theaccumulation part is charged approximately to the level of the sourcevoltage, so that the accumulation is cleared. Thereafter, when theintegration clear gate pulse ICG is dropped to a LOW level, the MOS gateis brought into an opened state, thereby discharging the electric chargefrom the accumulation part, which has been charged to the level of thesource voltage, by the photocurrent corresponding to the imagebrightness distribution generated in the photodiode array. Thus, theinformation of the brightness distribution will be accumulated in thepicture element array.

The MOS gate is provide between the charge accumulation part and theregister in each CCD block of the standard area and the reference area.The MOS gates are closed when they are applied with HIGH level SH pulsesSH1-SH4, respectively, and the electric charges, accumulated after theapplication of the integration clear gate pulse ICG to the accumulatingpart, are transferred to the respective registers.

A DOS circuit is provided for compensating the outputs of monitoroutputs AGCOS1-AGCOS4. The DOS circuit is formed by a capacitor C5 and abuffer having the same characteristic as the capacitor and the buffer ofthe monitor output part, with its input terminals being opened. Thecharged voltage approximately to the source voltage in response to theintegration clear gate pulse ICG is maintained by the DOS circuit evenafter the disappearance of the integration clear gate pulse ICG.

The difference between the example shown in FIGS. 12a and that shown inFIG. 12b will be explained.

Examples shown in FIGS. 12a and 12b differ from each other in thearrangement of the CCD registers and the succeeding output stages of theCCD registers. In FIG. 12a, a CCD register Rg is arranged in series withrespect to each zone, with an output buffer being provided at the end ofthe CCD register Rg. The CCD register Rg sequentially produce outputs inthe order of the standard area in the first zone, the standard area inthe second zone, the reference area in the first zone, the referencearea in the second zone, the reference area in the fourth zone, hereference area in the third zone, the standard area in the fourth zoneand the standard area in the third zone in synchronization with thenegative edge of a transfer clock φ1.

On the other hand, the CCD image sensor shown in FIG. 12b is arranged inparallel structure such that each zone has a different register, and atthe end of each register, an output buffer is connected. Thus, there arefour buffers in total. Outputs of the standard area and the referencearea in the first to fourth zones are sequentially outputted from thefirst to fourth buffer outputs respectively, in synchronous relationwith the negative edge of the transfer clock φ1.

Moreover, in the CCD image sensor, since control is carried out in theintegration time which is different in the four zones, in the case ofFIG. 12a a picture elements indicated by hatched lines is shielded by analuminum mask, and such a mask is provided at an output end of each ofthe standard area and the reference area in each zone, so as to correctoutputs from the picture elements carrying error signals caused by thedark output level which is greatly changed by the temperatures and theintegration time. In the case of FIG. 12b, the adjusting pictureelements for adjusting the dark output level are provided at an outputend portion of only standard area in each zone, and are used to adjustthe output levels of both the standard area and the reference area ofeach zone.

Next, the AF interface AFIF and the CCD image sensor will be described.

A method for driving the CCD image sensor shown in FIG. 12a havingseries-connected type CCD register, will be described below inconnection with FIG. 13. In FIG. 13, the left-hand side thereof shows aconnection part with the CCD image sensor, while the right-hand sidethereof shows a connection part with the AF microcomputer AFP. The firstCCD integration, after the start of the AF operation, requires outputsfrom all zones. The integration at this stage is started by theapplication of the integration clear gate pulse ICG from the AFmicrocomputer AFP. By the application of the integration clear gatepulse, all the picture element accumulation parts and the monitoroutputs of the CCD are initialized. After the pulse disappears, both theaccumulation parts and the monitor outputs start the accumulation ofphotoelectric currents.

An AF timing control circuit AFTC, which receives an original clock φ0from the AF microcomputer AFP and a divided clock φa prepared bydividing the original clock φ0, selects the clock φa having a frequencysuitable for he A/D conversion as a transfer clock, upon application ofa command signal, i.e., the AF zone selection signal AFZS from the AFmicrocomputer AFP, for selecting every zone. The integration clear gatepulse ICG is inputted to a reset input of an R/S flip-flop. Therefore,the R/S flip-flop is reset, so that the transfer clocks φ1 and φ2 to beapplied to the CCD are maintained, respectively, at a HIGH level and aLOW level. Under this condition, the accumulation in the pictureelements proceeds, and at the same time, the accumulation in the monitoris carried out similarly. Thus, a monitor output, which is dropped by aconstant level V1 below the compensation output, starts to be produced.The value V1 is previously set so that the electric charges accumulatedin the picture element accumulation part are at an average output levelsuitable for the A/D conversion and focus detection calculation effectedat a later stage.

Sequentially from the zone receiving higher brightness of the object,each of comparators COM11-COM14 produces a HIGH level signal when theinput signal to the inverting input exceeds the level V1. The HIGH levelsignal is applied through an OR gate to a one-shot pulse generator,which thereupon produces a shift pulse SHi (i=1,2,3,4). Each of theshift pulses SH1-SH4 is applied to the CCD image sensor for shifting theelectric charges in the picture element accumulation part to respectivetransferring register. However, since the transfer clock is not suppliedto the register, the electric charges corresponding to the potentials inthe picture elements are held in the register. In the above-describedmanner, when all of the comparators COM11-COM14 produce HIGH levelsignals, i.e., when the output TINT of an AND gate becomes HIGH, theregister in each zone is stored with an appropriate average levelsignal. When the output TINT of the AND gate produces a HIGH levelsignal, such a HIGH level signal is used as a signal informing the AFmicrocomputer of the completion of the integration in all zones of theCCD image sensor. Also, the TINT output, after being applied through theOR gate and the delay circuit to R/S flip-flop, is used as a startsignal for starting the application of the transfer clock. A waveform ofthe outputs is illustrated in FIG. 14. Thereafter, each picture elementoutput is generated from the OS terminal in synchronization with thenegative edge of clock φ1. The AF timing control circuit AFTC generatesa sampling signal φb by counting φ2 at respective timing when thepicture element for adjusting dark output is generated, with supplyingan AD start signal ADS to the AD converter ADC.

Thus, the dark output adjustment of the output of the CCD appropriatefor the respective integration time is sequentially carried out in theorder from the standard area in the first zone, the second zone standardarea, the first zone reference area, the second zone reference area, thefourth zone reference area, the third zone reference area, the fourthzone standard area and the third zone reference area, and thereafter theoutputs are A/D converted. Then, in synchronism with an A/D conversioncompletion signal EOC, A/D converted signals are inputted to the AFmicrocomputer AFP.

The integration drive for the selected zone as effected in step #127 ofFIG. 5 will be described with reference to the circuit of FIG. 13.

When the zone signal SZS is sent to the AF timing control circuit AFTC,a number of transfer clocks required before the signal generation fromthe zone are set in a counter provided in the circuit AFTC. After theapplication of the integration clear gate pulse ICG, the AFmicrocomputer AFP selects an output from outputs TINT1-TINT4 of themonitoring comparators COM11-COM14 in the block desired to be outputted.Simultaneously with the generation of a HIGH level signal from thecomparator, a manual shift signal SHM is generated to cancel the stop ofthe transfer clocks φ1 and φ2. The AF timing control circuit AFTC whosecounter has been set counts the clock φa, so that the original clock φ0is supplied to the CCD until the counter counts a number equal to theset number. A clock for the A/D conversion is supplied to the CCD onlywhen the selected zone produces output. Also, AF microcomputer AFP issupplied with the data only related to the selected zone in synchronousrelation with the AFD conversion completion signal EOC. Then the counteris set again. When the other zone produces output, transfer is performedat a high speed. A similar operation is carried out when the remainingpicture elements in the attended zone are processed. Thus, in the manneras described above, the waste time such as during the damping time andthe integration time of the data can be reduced, thereby enabling a fastAF operation. The timing chart of the above-described operation isillustrated in FIG. 15.

Finally, a method for driving the CCD image sensor having CCD registersconnected in parallel relation as shown in FIG. 12b, will be explainedin connection with FIG. 16.

In FIG. 16, at the left-hand side thereof the CCD image sensor is shown;at the right-hand side thereof from the multiplexer MPX an AF interfaceAFIF is shown, and the terminal arrays at the right-hand side thereofare connected to AF microcomputer AFP.

According to the CCD image sensor of FIG. 16, it is possible to reducethe operating time by a special dividing method for effecting the firstdrive of every zone in the CCD after the start of the AF operation, asdescribe below. The AF microcomputer AFP produces the integration cleargate pulse ICG so as to remove the electric charge accumulated in eachof the picture element accumulation parts and the monitors. At thistime, by the zone signal ZS indicating the first zone, an input signalAGCOS1 is generated from an output terminal ACOS0 of the multiplexerMPX, and an input signal SH0 is generated from an output terminal SH1,and an input signal OS1 is generated from an output terminal OS0.

The signal AGCOS1 is monitored by the comparator COM2 through themultiplexer so as to monitor the accumulation of the electric charge ofthe CCD image sensor for the first zone. As the accumulation of theelectric charge in the monitoring part and each picture element part ofthe first zone is advanced, and the signal AGCOS1 reaches the level V1suitable for a later analog processing circuit and a later focusdetection calculation, comparator COM20 produces a signal which causesthe generation of the shift pulse SH0. The shift pulse SH0 is providedthrough the multiplexer MPX, to the CCD image sensor of the first zoneas the shift pulse SH1. When the predetermined maximum integration timehas passed without reaching of the signal AGCOS1 to the level V1, themanual shift pulse SHM is applied from the AF microcomputer AFP tomultiplexer MPX a the shift pulse SH0. Thereupon, multiplexer MPXsupplies the shift pulse SH1 to the CCD image sensor of the first zone.

As a result of the supply of the shift pulse SH1, the CCD image sensorof the first zone terminates the operation for accumulation of theelectric charge, and accordingly, the electric charges accumulated inthe picture element accumulation part are shifted, through the shiftgate, to the CCD shift register Rg1 of the first zone.

At this time, an input signal applied to a delay and one-shot circuit DOfor generating the shift pulse SH0 is also applied to the transfer clockgenerating circuit TCG, which generates two transfer clocks φ1 and φ2,the pulse phase is so arranged that the shift pulse SH1 is supplied tothe CCD image sensor of the first zone while the transfer clock φ1 is ina HIGH level. In synchronization with the negative edge of the transferclock φ1, the photoelectric output signal OS1 of an image as accumulatedin the first zone of the CCD image sensor is sequentially outputted oneafter another through the output terminal OS0 of the multiplexer MPX.

Immediately after the generation of the shift pulse SH0, the AFmicrocomputer AFP supplies the second integration clear gate pulse ICGto the CCD image sensor. The second integration clear gate pulse is anintegration start signal to the CCD image sensor of the second zone, bywhich the accumulation operation f the electric charge in the monitorpart and the picture element part of the second zone and the dischargingoperation of the accumulated electric charge are continuously conductedimmediately after the completion of the accumulation operation of theelectric charge in the first zone.

Thereafter, among the photoelectric output signals OS1 in the firstzone, the output of the picture element for adjusting dark output isstored in a sample and hold circuit S/H in accordance with the controlof the AF microcomputer AFP. Thereafter, each picture element outputsignal is subtracted by the stored output signal of the picture elementfor adjusting dark output, and the obtained difference is inputted asthe image information.

In this case, when the accumulation of the electric charge in the CCDimage sensor has been forcibly terminated by the manual shift pulse SHMfrom the AF microcomputer AFP, an automatic gain adjusting circuit AGCautomatically adjusts the gain in accordance with the averageaccumulation level of the output in the monitor part by the use of theoutput of comparators COM20-COM22. In other words, outputs both from thephotoelectric output OS0 and from the sample and hold circuit S/H areinputted to the automatic gain adjusting circuit AGC, and the differencetherebetween is suitably amplified and outputted. The output of theautomatic gain adjusting circuit AGC is inputted to the A/D convertingcircuit ADC and the converted digital signal is inputted to the AFmicrocomputer AFP as the image information. After the image informationof the first zone is inputted to the AF microcomputer AFP in theabove-described manner, the condition is detected of the accumulation ofthe electric charge of the CCD image sensor in the second zone which hasbeen started previously. To this end, AF microcomputer AFP provides aLOW level signal of the signal TINTC so as to prohibit the manual shiftpulse SHM to be used as the shift pulse SH0, and also the zone signal ZSis switched from the first zone to the second zone. As a result, theinput signal AGCOS2 is outputted from the output terminal AGCOS0 of themultiplexer MPX, and the input signal SH0 is outputted from the outputterminal SH2, and also, the input signal OS2 is outputted from theoutput terminal OS0.

Then, the AF microcomputer AFP confirms the signal TINT0. If the signalTINT0 is HIGH, the CCD image sensor in the second zone is alreadycharged to a level greater than a certain level, so that the integrationclear gate pulse ICG is supplied to the CCD image sensor again to startthe accumulation of the electric charge in the CCD image sensor of thesecond zone again. On the contrary, when the signal TINT0 is LOW, theaccumulation of the electric charges in the CCD image sensor of thesecond zone is not completed while the image information is being takeninto the AF microcomputer AFP of the CCD image sensor of the first zone.Therefore, the AF microcomputer AFP changes the TINTC to be HIGH again,waiting for the signal TINT0 to become HIGH. When the signal TINT0 ischarged to a HIGH level, or in the case where a predetermined maximumcharge accumulation time has elapsed, the shift pulse SH is generatedand the accumulation of the electric charge in the CCD image sensor ofthe second zone is completed. Here, the predetermined maximum chargeaccumulation time is equal to a sum of the time required to receive theimage information of the CCD image sensor of the first zone by AFmicrocomputer AFP and the time needed for the signal TINT0 to become aHIGH level signal. In a similar manner, the charge accumulation of theCCD image sensor and the image information being received from the CCDimage sensor are carried out for all zones in a certain order such as:the starting of the charge accumulation of the CCD image sensor in thethird zone; the image information being received from the CCD imagesensor in the second zone; detection of the condition of chargeaccumulation in the CCD image sensor in the third zone; and so on.

In the case where a long charge accumulation time is required such aswhen the object to be photographed has a low brightness, the CCD drivingtime is shorted by a time represented by a formula

    (image information receiving time)×{(number of zones)-1}.

However, in the case where the object to be photographed is not low inbrightness and accordingly a long charge accumulation time is notnecessary, the CCD driving time will not be shortened.

In the circuit construction shown in FIG. 12b, a buffer part and a shiftgate part may be provided between the gates SHG1-SHG4 and the registersRg1-Rg4, respectively. When such an arrangement is employed, the firstshifting operation of the accumulated charge from the accumulation partto the buffer is conducted upon completion of the charge accumulation,even when the object has a high brightness. In the case where theintegration completion signal TINT0 has been already generated at thetime of the above detection of the charge accumulation condition, theelectric charge may be shifted for the second time from the buffer partto the registers Rg1-Rg4, thereby shortening the CCD driving time.

Also, in the circuit construction shown in. FIG. 12a, the buffer partand the shift gate part similar to those provided in the circuit of FIG.12b may be added. When this arrangement is employed, the complicatedcircuit operation, such as to stop the generation of the transfer clockφ1 during the charge accumulation operation can be simplified, and atthe same time, noise signals caused by such a complicated operation canbe suppressed.

Furthermore, although the camera of the above-described embodiment isthe so-called AF priority type in which the shutter release is permittedwhen the lens is brought into the in-focus condition, the presentinvention is not restricted to this, but may be applied to a camera of ashutter release priority type in which the shutter is released by theshutter-release operation which is done irrespective of the fact whetheror not the camera is in the in-focus condition.

Moreover, it is not necessarily required that the focus detectionsensitive zone corresponding to the AF zone exactly coincides with thelight measuring sensitive zone for controlling the exposure. Forexample, one sensitive zone for measuring light can cover a wider rangeincluding one focus detection sensitive zone. Alternatively, one lightmeasuring sensitive zone excluding the center of the photographing rangemay be arranged to cover a plurality of the focus detection sensitivezones. In the latter case, it may be so constructed that any one of theplurality of the focus detection sensitive zones can be covered by onelight measuring sensitive zone. Further, in order to monitor thecondition of the charge accumulation of the respective CCD imagesensors, the monitor output may be used as a light measuring signal.Also, the monitor output for monitoring the condition of the chargeaccumulation of the CCD image sensor of the selected focus detectionsensitive zone may be utilized as the information of the light measuringsensitive zone selected in correspondence to the above focus detectionsensitive zone.

Furthermore, although the focus adjustment according to the embodimentdescribed above is arranged to give the highest priority to the AF zonein which an object located closest to the camera is contained, instead,it may be so arranged that the lens is automatically focused to anintermediate point between an object located closest to the camera andan object located farthest from the camera, or to an object locatedfarthest from the camera. Furthermore, it may be possible to selectivelychange the priority of the zones. In this case, it may be so decided atthe designing occasion of the camera as to whether the switching of thezone is necessary, on the basis of statistical data of the generalphotographic situations, such that the most suitable zone for generalphotographing is selected.

According to the present invention, the focusing condition of thepicture-taking lens is detected in multi-zones or multi-points withinthe photographing frame. Of the plurality of zones or points, the cameraautomatically selects a particular zone or point, e.g., the zone orpoint in the photographing frame containing an object located closest tothe camera. The camera further selects, from a plurality of lightmeasuring zones, a particular light measuring zone which is located at aplace coinciding to the selected focus zone, or at a place covering theselected focus zone so as to use the obtained data for displaying orcontrolling the exposure. Accordingly, even when the target object isnot located at the center of the photographing frame, the exposure canbe controlled and display on the basis of the light measuring data withrespect to the target object, with no special operation, such as an AElock operation. Consequently, even when the target object is moving andit is difficult to catch the object at the center of the photographingframe, the exposure data display or the exposure control based on thespot light measuring data with respect to the target object can beconducted with higher possibilities. Moreover, since the exposure isdetermined by the value of the spot light measuring, the calculatedexposure data is less influenced by the brightness in the environment.

Although the present invention has been fully described by way ofexample with reference to the accompanying drawings, it is to be notedhere that various changes and modifications will be apparent to thoseskilled in the art. Therefore, unless otherwise such changes andmodifications depart from the scope of the present invention, theyshould be construed as being included therein.

What is claimed is:
 1. A camera with a multi-zone focus detecting devicecomprising:an objective lens mounted on a camera; means for detectingfocusing conditions in a plurality of zones in a photographing field tobe photographed, based on light which has been passed through saidobjective lens so as to produce a plurality of focusing condition data;means for selecting one zone based on the result of the focusingconditions, provided that a certain condition is satisfied; means fordetecting whether or not said selecting means is selecting one zone;means for measuring light in an area corresponding to said selected zonebased on light which has passed through said objective lens as a spotlight data; means for measuring light in said image as an average lightdata; means for choosing said spot light data when said detecting meansdetects that one zone is selected, and said average light data when saiddetecting means detects that no zone is selected; and means forcalculating exposure data based on said chosen data.
 2. A camera with amulti-zone focus detecting device, comprising:an objective lens mountedon a camera; means for receiving light, passing through said objectivelens, and coming from a plurality of zones in a photographing field tobe photographed to produce a plurality of light receiving signals; meansfor detecting focusing conditions of said objective lens in saidplurality of zones on the basis of said plurality of light receivingsignals to produce a plurality of focusing condition data; means forproducing one focusing condition signal determining in accordance withsaid plurality of focusing condition data; means for driving saidobjective lens to an in-focus position in accordance with said focusingcondition signal; means, different from said receiving means, formeasuring light passed through said objective lens in a plurality ofareas; means for generating a plurality of measured light data eachcorresponding to each of the amounts of light in each of said pluralityof areas measured by said measuring means; means for forming an exposurecontrol data on the basis of said plurality of measured light data, andmeans for repeatedly operating said focusing condition detecting means,said measured light data generating means and said exposure control dataforming means until said objective lens is driven to said in-focusposition.
 3. A camera as claimed in claim 2, wherein said one focusingcondition producing means include means for selecting one focusingcondition data among said plurality of focusing condition data.
 4. Acamera as claimed in claim 3, wherein each area corresponds to each zonerespectively, and wherein said exposure control data forming meansincludes means for calculating an exposure control data based on onemeasured light data of one area corresponding to one zone whose focusingcondition data is selected by said selecting means.
 5. A camera asclaimed in claim 4, further comprising means for storing, when saidobjective lens is driven to said in-focus position, one measured lightdata obtained from one area corresponding to said selected zone, andwherein said calculating means calculates said exposure condition databased on said one measured light data stored in said storing means.
 6. Acamera as claimed in claim 2, further comprising means fordiscriminating whether or no said one focusing condition producing meansalready forms one focusing condition data, and means for measuringaveraged light in said photographing field based on the light which hasbeen passed through said objective lens so as to produce an averagedlight data, and wherein said exposure control data forming means formsan exposure control data based on said averaged light data when saiddiscriminating means discriminates that the one focusing conditionproducing means has not yet formed one focusing condition data.
 7. Acamera with a multi-zone focus detecting device comprising:an objectivelens mounted on said camera; means for detecting a focusing condition ina plurality of zones in a photographing field to be photographed fromlight which has passed through said objective less, and for producing aplurality of focusing condition data; means for selecting one of thezones from the focusing condition data; means for measuring brightnessin a plurality of areas from light which has passed through saidobjective lens, and for producing a plurality of brightness data; meansfor repeatedly inputting the brightness data from said measuring means;means for driving said objective lens to an in-focus condition on thebasis of focusing condition data obtained from the selected zone; meansfor storing the brightness data; means for updating the contents of saidstoring means every time that brightness data is inputted; means forinhibiting said updating means from updating the contents of saidstoring means when said objective lens is driven to the in-focuscondition; means for calculating exposure data based on the brightnessdata stored in said storing means in accordance with one of plurality ofpredetermined different modes of exposure calculation, and means fordetermining the specific mode of exposure calculation including takinginto consideration, when relevant, the results of the selection by themeans for selecting a zone in the photographing field.
 8. A camera witha multi-zone focus detecting device comprising:an objective lens mountedon said camera; first light receiving means having a plurality of firstreceiving elements, each of which generates a first signal in accordancewith light incident thereon, the light coming through said objectivelens from one of a plurality of zones in a photographing field to bephotographed, respectively; means for detecting a focusing condition ineach zone in accordance with the first signal to output focusingcondition data; means for selecting one of the zones in accordance withthe focusing condition data; second light receiving means having aplurality of second receiving elements, each of which generates a secondsignal in accordance with light incident thereon, the light comingthrough said objective lens from one of a plurality of areas; means forgenerating a third signal indicating whether or not the selection ofsaid selecting means is completed; means for making a first calculation,when he third signal indicates that the selection is completed, toobtain brightness data in accordance with the second signals, and makinga second calculation which is different from the first calculation, whenthe third signal indicates that the selection has not yet beencompleted, to obtain brightness data in accordance with the secondsignals, and means for calculating exposure data in accordance with thebrightness data.
 9. A camera as claimed in claim 8, furthercomprising:means for determining whether or not there is a zone wherethe focusing condition cannot be detected, wherein said generating meansgenerates, in response to the determining means, the third signalindicating that the selection has not yet been completed when there isno zone where the focusing condition can be detected.
 10. A camera asclammed in claim 8, wherein the first calculation is made in accordancewith the second signal generated by one of he second receiving elementswhich receives light from the area corresponding to the selected zone.11. A camera with a multi-zone focus detecting device comprising:anobjective lens mounted on said camera; means for detecting a focusingcondition in a plurality of zones in a photographing field to bephotographed from light which has passed through said objective lens,and for producing a plurality of focusing condition data; means forselecting one of the zones from the focusing condition data; means formeasuring brightness in a plurality of areas from light which has passedthrough said objective lens, and for producing a plurality of brightnesssignals; means for generating a signal indicating whether or not saidselecting means has selected one of the zones; means for making a firstcalculation based on the brightness signals to obtain first brightnessdata when the signal generated by said generating means indicates thatsaid selecting means has selected one of the zones, and making a secondcalculation, which is different from the first calculation, based on thebrightness signals to obtain second brightness data when the signalgenerated by said generating means indicates that said selecting meanshas not yet selected one of the zones, and means for calculatingexposure data on the brightness data outputted from said making means.12. A camera as claimed in claim 11, wherein said generating meansgenerates the signal indicating that said selecting means has not yetselected one of the zones until the detection of a focusing conditionand the selection of one of the zones are completed.
 13. A camera asclaimed in claim 11, wherein said generating means generates the signalindicating that said selecting means has not yet selected one of thezones when a focusing condition cannot be detected in any one.
 14. Acamera as claimed in claim 11, wherein the first calculation is made onthe brightness signal obtained from the area corresponding to theselected zone.
 15. A camera as clammed in claim 14, wherein the firstcalculation is made on only the brightness signal obtained from the areacorresponding to the selected zone.
 16. A camera as claimed in claim 11,wherein the second calculation is made to calculate the average of allthe brightness signals.